Primary drinking water standards:

Primary standards and treatment techniques protect public health by limiting the levels of contaminants in drinking water.MicroorganismsDisinfectantsDisinfection ByproductsInorganic ChemicalsOrganic ChemicalsRadionuclides

Maximum Contaminant Level Goal (MCLG) – The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals.Maximum Contaminant Level (MCL) – The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards.Maximum Residual Disinfectant Level Goal (MRDLG) – The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants.Treatment Technique (TT) – A required process intended to reduce the level of a contaminant in drinking water.Maximum Residual Disinfectant Level (MRDL) – The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.

The National Primary Drinking Water Regulations (NPDWR) are here:

Contaminant MCLG1 (mg/L)2 MCL or TT1 (mg/L)2 Potential Health Effects from Long-Term Exposure Above the MCL (unless specified as short-term) Sources of Contaminant in Drinking WaterCryptosporidium zero TT3 Gastrointestinal illness (such as diarrhea, vomiting, and cramps)Human and animal fecal wasteGiardia lamblia zero TT3 Gastrointestinal illness (such as diarrhea, vomiting, and cramps)Human and animal fecal wasteHeterotrophic plate count (HPC) n/a TT3 HPC has no health effects; it is an analytic method used to measure the variety of bacteria that are common in water. The lower the concentration of bacteria in drinking water, the better maintained the water system is.HPC measures a range of bacteria that are naturally present in the environmentLegionella zero TT3 Legionnaire’s Disease, a type of pneumoniaFound naturally in water; multiplies in heating systemsTotal Coliforms (including fecal coliform and E. Coli)Quick reference guidezero 5.0%4 Not a health threat in itself; it is used to indicate whether other potentially harmful bacteria may be present5Coliforms are naturally present in the environment; as well as feces; fecal coliforms and E. coli only come from human and animal fecal waste.